Automatic dishwashing machines are widely used in commercial applications and now also are commonplace in most homes. Typically, dishes in such machines are deposited in open wire work baskets or dishware racks located above upwardly and laterally directed jets of cleaning fluid. In most home dishwashers, the jets of cleaning fluid are upwardly projected from a rotatable spray; arm and the fluid exerts considerable upward force on the various articles placed on the dishware rack. Bowls, glasses, cups, saucers, pitchers and the like are placed on the racks with the inside or hollow side facing downwardly for direct impingement by the high-pressure fluid projected from the cleaning jets.
A combination of the strength of the chemicals in the cleaning fluid and the pressure of the fluid jets results in the cleaning of the various dishes. Jets of higher pressure are preferred for items which are difficult to clean, that is, items which have food particles adhereing to them. High pressure jets, however, tend to lift and turn over dishes, particularly lightweight dishes, causing the dishes to be turned over and leave the hollow side facing upwardly away from the impact of the high pressure fluid jets. When this occurs, the inside of such dishes are not cleaned and they tend to become filled with wash water splashing off the walls and the top of the cleaning compartments of the dishwasher. If the pressure of the fluid jets is lessened to prevent the turning over of lightweight dishes, the cleaning action of the dishwasher is correspondingly reduced. To overcome the reduction in cleaning action which occurs, stronger cleaning solutions may be employed, but strong cleaning solutions tend to harm some dishes or the finish on the dishes.
Another result of the use of high pressure jets of cleaning solution or fluid is that, even if the dishes are not turned over. They tend to shift about in the dishware rack or basket and bounce against one another. For fragile dishes, the result of such movement can result in breaking or chipping of the dishes. This obviously is undesirable.
In an effort to overcome the tendency for some dishes, particularly lightweight dishes, to be overturned by high pressure jets of fluid, devices have been developed for commercial dishwashers to hold the dishes in place on the rack during the washing cycle. Two patents which are directed to systems for accomplishing this result are the U.S. Pat. to Randall No. 3,616,806 and Murray No. 4,006,950. Both of these patents are directed to commercial dishwashes where a relatively heavy, limp, metal mesh is lowered on top of the articles placed in the rack in the dishwasher. The weight of the metal mesh on top of the articles prevents them from moving from the position in which they are placed during the washing action of the dishwasher. In the Murray Patent, the mesh is automatically raised and lowered in response to the movement of the work basket as the basket is withdrawn and inserted into the machine. In the device of the Randall Patent, the mesh is in the form of several transverse bands which are wound up on support shafts at the sides of the machine interior. After the articles to be washed are placed on the washing rack, the support shafts are rotated to unwind the mesh bands and lower them onto the tops of the articles on the washing rack. The devices disclosed in both of the these patents are quite complex, requiring additional mechanical parts to be mounted in the interior of the dishwasher cleaning chamber. The heavy metal hold-down mesh also is cumbersome and remains within the machine at all times.
Four other patents which are directed to attempts to prevent the movement of dishes as a result of the force of the cleaning fluid in a dishwasher, are the U.S. Patents to Kauffman No. 3,289,854; Davis No. 2,899,079; Opal No. 3,901,728; and Mason No. 3,612,285. All four of these patents are directed rigid hold-down devices for retaining articles in place on the rack of a dishwasher. In Kauffman, the device is a clip which presses a glass or cup against an upright post. In Davis, a rigid hold-down perforated cover is employed. In the Opal Patent, a movable disk is rotated down over cups and articles to be held in place; and the device disclosed in the Mason Patent is an arrangement of pivoted retainer rods. All of these devices are connected in some way or another to the dishwasher interior or to the rack, and all of them are rigid devices or clamps for placing pressure on the top or sides of the article to be held in place. This prevents movement of the articles to be cleans when they are subjected to the pressure of the high pressure jets of cleaning fluid.
It is desirable to provide a simple and effective hold-down device for a dishwasher which is capable of securely holding lightweight articles in place on the dishwasher rack during the washing operation. It further is desirable for such a hold-down device to be inexpensive, simple to construct and to use, without requiring any modification of a standard dishwasher.